Telephone system



April 16, 1929. E, VROOM ET Ax. 1,708,983

' TELEPHONE SYSTEM Filed Aug. 17, 1926 7 Sheets-Shesffl l ffy. U 22 23 SUV 'U 37? uw Ooo Q UH @a @4 @d 3 Aprill 16, 1929. E. vRooM z-:TAL 1,708,983

TELEPHONE SYSTEM Filed Aug. 17, 1926 7 Sheets-Sheet 2 April 16,k 1929. E. vRooM ET AL. 1,708,983

TELEPHONE SYSTEM Filed Aug. 17, 1926 '7 Sheets-Sheet 3 MA RGINAL VON 302 MARGINAL Apil165'1929. E. VROOM ET'AL 1,708,983

TELEPHONE SYSTEM Filed Aug. 17, 192e v sheets-sheet 4 April 16, 1929. E. vRooM ET AL 1,708,983

TELEPHONE SYSTEM Filed Aug. 17, 1926 '7 sheets-sheet 5 REPEATER-G y W m34 April 16, 1929. v E. vRooM ET AL 1,708,983

` TELEPHONE SYSTEM Filed Aug. 1'?, 1926 'T Sheets-Sheet 6 April-16, 1929. E. vRooM ET Al. 1,708,983

TELEPHONE SYSTEM I Filed Au'g. 17, 1926 '7 sheets-sheet v oo u J mit n fnl/enfans fda/grd Vrana/77 fer mafia/5' i2/Z tl ll latented Apr.. 16, 1929.

:ann/'eran vaccin, er essrnrne, sun Fenomeno s. nuez, on MOUNT Vennen, NEW tenir, 'ro ser@ frjnnnrrronn Lenen-.aromas INCORPORATED, or new Yoan, n. Y., a consonantes or' new Your..

TELEPHONE SYSTEM.

Application 'filed August 17, 1926. Serial No. 129,683.`

'.,l`his invention relates to telephone exchange switching systems and more particularly to the automatic selection et speech amplifying and repeating apparatus and the.

No. 529,682, tiled lling. ll', 1952.6, have been devi A.d 'lor automatacallf,7 inserting` repeatingl amplifiers in toll connections. lu these cases toll cord. circuits are arranged tor toll lines that do not require the addition ot re peaters and toll lines that do require such an addition. In general, the arrangen'ient is such that an automatic discrimination is made between the two kinds of toll lines when a cord circuit is employed to interconnect the toll lines. "W hen a repeater is required, this discriininatingi1 arrangement functions to start the automatic selection and connection of the repeater between two lines. A selectine; mechanism or repeater selector is associated with each cord circuit so arranged as to be automatically started by the discriininatingi` means to hunt 'for and connect the associated cord circuit with an idle repeater, a pluralit),7 ot' repeaters being provided `for the coinmfni use olf said cord circuits, ln the last mentioned copending` application the connection between the lines and repeater` is accomplished by means of links comprising two switches oli the line iinder type with their brushes connected together. rlhe arrangen nient is such that when a cord circuit has been connected between two lines and an idle repeater has been tound, the switches of one link are actuated to connect one ofi the lines with the incoming;v end oli the selected repeater, while siinultaneinisly, the switches of another link are actuated to connectthe other line with the outgoing` end ci the selected repeater.

According to the present invention each toll line is equipped with a selective switch which responds automaticalljyv when the line is taken in use to connect such line, depend `ing,1 on whether it is calling or being` called, to one or the other sede oit a selected idle rei V i igiealer. lhus when a calling and a called line are taken in use by an operator to extend a toll call the corresponding; selective switches ci frate simultaneously to include the `selected repeater in the toll connection. In such a system toll lines are divided in coniparatively small groups, each toll line being provided with a switch, hereinafter called the trunk selector, having access to a pluralit;T et trunks, each trunk being connected to a line finder switch, hereinafter called the repeater linder, having' access to a plurality of repeater units. Each trunk selector is ai ranged to connect the associated. line with an idle trunk in either of two groups, the trunks in one group leadinpjto repeater linders bowing` access to the incoming),` ends of repeaters and the trunks in the other group leading` to repeater finders having access to the outgoing` ends oi repeaters.

T his switching` and. grouping arrangement is applied to a system in which an idle peater may be selected by means Asimilar to the arrangement shown in the last inentioned copending application, the arrangement being such that when a cord circuit is connected between two lines requiring;` a repeater inserted between them, the repeater selector associated with this cord is actuated to select an `idle repeater. The cord circuits may also be arranged in groups withv each repeater selector haring' access to a certain number ot the total number oil repeaters available to all ol the'cord circuits in the group. TWhen, therefore, a cord circuit has been connected between two lines and. an idle repeater has been found, `the trunk selectors associated with said lines are antouiaticalW ly and simultaneously actuated to select trunks. The selector associated with the call originating lino will select a trunk associated with a repeater .finder hs'iviugg access to the incoming' `end el the selected repeater', said repeater linder in turn beinel actuated to lind the repeater and connect itwith the call orio'- inatino` line. On theother hand the selector associated with the desired line will select a trunk associated with a repeater finder haw ing,` access to the outgoing` end ot the sel ectod repeater, said repeater linder in turn beine' actuated to find the repeater and connect it with the desired line. This arrangement, tllerelore, is particularl)T adapted and suitable or small exchange installations that are only likely to grow to a moderate size. It should ybe understood that the expressions incoming and outgoing ends of repeaters are merely used for convenience in distinguishing betweenthe lineend to which the various switches have access Yand does not refer tothe transmission characteristics of the repeater.

This invention has been illustrated in the accompanying drawings, in which;

Fig. l is a diagrammatic representation of a typical grouping arrangement of the toll lines, trunk selectors, repeater finders, cord circuits and repeater selectors;

Fig.t2 illustrates the incomingr end of one toll line requiring the addition of a repeuter; f y

'-Fig. 3 illustrates the .trunkselector associated with the toll line shown in Fig. 2 and two repeater inders havingaccess respectively to vtheincoming and outgoing ends of repeaters with their respective trunks terminating in the banks of the trunk selector shown int-his tigure;

Figs. 4 and 5 illustrate a cord circuit and its associatedrepeater selector and a. repeater, the repeaterfbemg merely indicated by means of an inclosure. These tigures also show various common circuits and switching arrangementsfor preventing more than one interconnection of toll lines from taking place at anyone time;

Fig. :6 illustrates the incoming end of another toll line requiring the addition of a repeater; while Fig. '7 shows the trunk selector associated with' the toll line shown in Fig. 6, a repeater fin-der having access tothe outgoing ends of repeaters, and a repeater linder having access to the incoming endsotl repeaters with their respective trunks terminating in the banks of the trunk selector shown in thisligure;

Fig. 8 shows the arrangement of the drawings .forming part of this application.

The general arrangement ot' the various equipments ior carrying out this invention may take the form shown in Fig. l. For example, the toll linesvmay be divided into three groups, 1, 2 and 3, with at() lines and thc Correspomling ynumber of trunk selectors such as 5 and 6 in groups -1 and Q and `with 20 lines andthe corresponding number of trunk selectors such'as 7 in group The trunkselectors such as and G may have accessto about 22 trunks, l1 of which will be connected to repeater finders such as 10 and l2 that have'access to incoming ends of repeaters, while the `other `l1 trunks may be connected to yrepeater linders such jas `1l andl that have access to outgoing ends -of repeaters. The trunk selectors at 7 wouldonly require y12 trunks, 6 of which would be connected to `repeater finders such as 1'5'hav1ng accessto incoming ends of re peaters, and the other 6 may be connected to repeater iinders such as 16 having access to outgoing ends of repeaters. The terminals of these repeater .finders may be connected to 24 repeaters such as 1S and multipled to all nders so that each repeater .finder will have access to all the repeaters. The 2l repeaters are represented at the terminal banks of repeater selectors such as 20 and 2l connected to diii'erentgroups ot' cord circuits such as 13;. and 23. The repeater selector terminalsl may be multipled in any convenient manner. lt is not necessary to have all of thc rclwatcrs available to each repeater selector' but a small number ot repeaters may be ci nnectcd to each group of repeater selectors, for example, l2 repeaters may be multipled to the terminals of selectors :20 and the other 12 to the selectors 21. It should be understood that any arrangement best suited to meet the comlitions in. any particular exchange may readily be made with this organization of switches and repeaters and that additions within rcasonable limits can be made without decreasingr the efiiciency of the system.

Referring now to Figures 2 to 7, the general scheme of interconnecting toll lines and inserting repeaters into these connections in accordance with this invention, will be outlined as follows: Let it be assumed that the toll line A is to be connected through a repeater with the toll line B and that cord circuit C to be used for the establishing of this connection. In accordance with the well known practice a call incoming over line A is observed by the inward operator on the usual toll board by the lighted lamp 200. After inserting the answering plu,"r of an ordinary cord circuit; into jack 201 of linc A. and communicating with the operator at the distant end of line A, it: is found that the call requires a through connection, this inward operator will switch the callV to a through opcrators position causing lamp 20;) to light. The through operator has access to a plurality of cords such as C, and observingr thc lamp Q02 of line A lighted, this operator inserts plug 00 of cord C into jack :203 ot line A and operates the talking kcy 1101. to connect; lier telephone set to line A for thc purpose of communicating with the operator at thc distant end to ascertain thc destination of the desiredl connection. After having rc ceivcd the desired information the through operator now inserts plug 403 into jack (500 ot line )i and restores the talking key 401.

As it has been assumed that both lilies A and B require the insertion of a repeater, these lines have special electrical characteristics on their sleeve circuits that will initiate, when the toll lines are connected to a cord circuit. automatic operations for the inserting of a repeater into the connection. For this purpose there is provided a so-ealled lockout selector switch or cord finder, one of which is lllU indicated at D. Each cord linder is coinnion to a position or group ot cords. Cord liiider D will new start to lind the cert C and. when 'found the cord finder reina-ins associated with the cord until the operations tor inserting a repeater in the connection are completed. rlhis is in order to prevent any other cord circuit in this group troni starting its operations until cord C is released. As soon as the cord linder D linds the cord circuit C, it starts operations to associate a secondary loclrout circuit or position finder indicated at E. rllhis linder is coininon to all the groups ot cords in the systein. 'lhe position linder lll remains associated with the cord circuit C until the coinplete sequence oi". operations t'or inserting a repeater into the connection has been etlected and functions to prevent any other cord circuit in any other `group troni startingl the selection ot a repeater until cord circuit C has conipleted'its functions in this respect. The association of the position linder takes place immediately, provided nootlier cord in the system is going through the process ot inserting' a repeater in a connection. rl1 he reason for the provision ot a cordliiider tor each group of cords and apposition linder tor all the groups ont cords in the system, is to insureV that only one connection ot a repeater between toll lines may talle place at anyone tiine. However, in order not to delay the connection ot repeaters any longer than is necessary, the cord linders ot the various groups ot cords iiiay operate to lind cords connectinp,l toll lines, independently and siiniltaneously and prepare the associated circuits to the point Where the coininen position linder begins to operate to perinit one cord circuit at a tiine to complete the repeater selecting` and connecting' functions.

@nce the cord C has assumed control over the position finder E it starts its repeater selector indicated at F to hunt tor an idle repeater. One ot' these repeaters has been indicated at inerely by incans ot an inclosure with all the leads troni' the repeater linders havini access to the incoming` end, troni the repeater finders havingl access to the outgoing;l

end et the repeater and trein the repeater selector lf shown leading into the saine. ils

the repeater itself orins no partoil the invention and as any repeater oit any well linoi e. type i'nay be used, it is thought that this representation will be sullicient. rllhe repeater selectors and the cord 4finder units inay be oil any Well known type hai/inn` a seriesY ot terminal banks with the brushes arranged to travel thereover in steps under control el' stepping` niagiiet niechanisnis. rlliese selectors and finders have no heine positions.

llVhen the repeater selector l? iinds an idle repeater, certain electrical conditions are established 'for the sleeve circuits ot the lines A and B tocause these lines to actuate their associated trunli selectors l'l and l, re-

spectively, to select idle trunks. In the case ol the trunk selector H, a trunk connected to a repeater hnder such as K having access to the incoming` end et the repeater C will be 1 v selected and in the case ci the trunk selector i. a trunli connected to a repeater linder such asL having access to the outgoingend ot the repeater G- will be selected. lt will be recalled that each trunk selector has access 'to two groups ol trunks connected ivi th repeater linders having access, respectively, to the in ,coming` and outgoing,I ends ot the coininon group ot repeaters. A trunk and repeater linder M companion to the repeater hurler K, and the repeater linder N companion to the repeater linder L have been shoivn in Fins. 3 and 7, respectively. The construction olf the trunk selectors l-l and l may be oit any well known type havingl a series ot terminal banks with brushes arranged to travel thereover in steps under control ot stepping` inaggiiet nicchaiiisins. These selectors have no heine positions. The construction ot the repeater tinders inay be ot any Well lrnoivn Strowgier type having terminal banks arranged in horizontal layers 'with brushes traveling; in a vertical liolloived by a horizontal step-by-step inoveinent.

In general, the connection ot the repeater G With lines A and B is accomplished by having, for example, the line A select through the trunk selector H, the trunk connected to repeater tinder l, and having); the repeater finder K hunt tor the incomingl end et the selected repeater G, and by having', lor ei;- ainple, the line B select through the trunk selector I, the trunk connected to repeater linder L, Which is actuated to hunt 'for the outgoing` end ot the selected repeater (l. lt should be pointed out at this tinie that the operations ot the trunk selectors ll and l and the repeater finders l and li are simultaneous so that no tinie is lost in lindng1 the repeater Cr to be interconnected between the lines A and B. i

`f^is soon as the lines have been connected through the repeater, the cord and position linders are released so that the cord linder lgiccoines available for other cords in the group to which cord C belongs and so that the position vliuder becomes available tor any other group ot this or any other position. Circuit changes will new tallo place to separate the tivo lilies trein the cord C and connect theui to the repeaters through the trunks inentioned and at the saine tiine connect the proper networks, hill/T, and Nl/V, in this cz se, to balance the lines and also to reniove certain short circuits in the repeater to inalre it operatiii'e. y

'l` ansniission inay then take place through the repeater While the connection to the cord circuit is opcnec. l-loivei'er, the usual ringino` bridge is lett across the toll line conductors so that supervisory signals `inay be Si l) lll! lill.)

ieu

received in the cordr circuit over the sleeve circuits. Arrang'en'ients are also made whereby vwhenever'the talking key of the cord circuit is operated, the repeater is cut out from t-he connection which,l under these circumstances, will extend through the cord circuit. Monitoring keys are also provided whereby connections from the repeater to the operators telephone set may be established through the repeater selector.

It either one of the plugs of the cord C iswithdrawn from the line jack, therepeater is released from the connection. peater lselector brushes, the cord finder brushes and the truuk. selector brushes remain in the position lin which they were last used., while the repeater finders are returned tofnormal positions.' The sleeve circuit of the line still connected to the cord remains in busy condition until both plugs are removed when the entire equipment is restored to its normal condition.

' For the purpose ot providing against failure of any part of thesysteni during the establishing of a connection involving a re- Y peater, a time delay circuit, indicated by T,

is used. yEach connection is allowed acertain time, for example live seconds, in which to be completed. If completed within this time the time ycircuit is restored to normal, but if it is not completed in this allotted time, thetime circuit functions to give an alarm indicating which cord circuit is involved, and also to cause the release ofthe cord finder involved to allow connections through another cord to take place. The arrang ment-s are also such that the toll operator receives a signal when all of the repeaters are busy. Cord circuits, such as C are also arranged or connecting ordinary toll lines that do not requireV the addition of repeaters. However', this invention is essentially con- Vcerned with the inclus-ion of repeaters in toll line connections and theV following detailed description will therefore be confined to the description of the functions taking place under such. conditions.

As stated, when a call comes in over line A, it is observed by thev inward operator at the usual toll board by the fact that the lamp I 200 is lighted. This lamp is lighted by a signal incoming over line A to operate relay 205 which causes the release ot relay 206 over 1 an obvious circuit. The release 0f relay 206 closes a circuit for the operationof relay 207 as follows: battery, middle winding ot relay 207, outer left hand armature and back contact oi relay 208, armature and back contact of relay 206 to ground. Relay 207 in: operating, closes a 'locking circuit for itself through itsright hand winding, armature and front Contact to battery at the makebeforesbreak contacts of' relay 208. A circuit is now also closed from this battery for vthelightingof1amp'200, over a circuitas folmomies lows: battery, n'iake-beforebreak Contact of relay 208, right hand armature and front cOntact or' relay 207, make-before-break contacts of relay 210, inner right hand armature and back contact of relay 211, lamp 200 to ground. The inward operator answers this call by inserting the answering plug of an ordinary cord circuit into jack 201 and connects 11er telephone set through this cord to line A. If it is found that the call requires a through connection, this inward operator transfers the call to a through operutors position.

It should be noted that the toll cord C shown in Fig. 3 may also be used by the inward operator forthis purpose. The transfer of the call to the through operators position, if a cord like C is used, may be accomplished by the operation of key 405 which causes battery to be applied to the ring spring of jack 201 for effecting the transfer. 1t should be understood that the talking kc y of the cord circuit used by this inward operator when operated to connect her telephone set to the line, causes the operation of relay 411. The operations in the cord circuit C, to cause this` elt'cct, will be described later. A circuit will now therefore be completed from battery, through relay 406 and the resistance 407 in parallel, through key 405, splitting key 410, lower middle armature and front contact of relay 411, ring terminals of the plug 400 and jack 201, retardation coil 213, left hand winding of relay 211, left hand winding of relay 210 to ground. The character of the winding oi relay 406 and of resistance 407 are such as to canse only the operation of relay 211 as relay 210 is marginal. The operation of relay 211 opens theI circuit for lamp 200 and transfers this circuit at the inner right hand armature and front contact of relay 211 to lamp 202 which lights at the through operator-s position. A locking circuit is provided tor relay 211 through its inner right hand armature and front contact to the battery at the make-before'breuk contacts of relay 208.

The lighting of lamp 202 indicates that a through connection is desired. The through operator now inserts plug 400 into jack 203 and the inward operator removes the plug corresponding to plug 400 from jack 201. The through operator then actuales thc talking key 401 to connect hcr telephone set to thc line A for the purpose of communicating with the operator at the distant end of toll line A to ascertain the destination of the desired connect-ion. The first etlecl. after the insertion of plug 400 into jack 203 and before the key 401 is operated, will lic the lighting of lamp 413 and the operation of relays 414 and 218 over a circuit as follows: battery, winding of relay 414, in parallel with battery through lamp 413, inner upper nor` mal contacts of key 401, left hand armature and back Contact of relay 416, sleeve terminals through its right hand armature and front contact to ground at the left hand armature and front Contact ofrelay 21S, and this relay '223 "in operating opens the circuit for relay 217. Relay 217 in releasing removes the battery from its left .hand armature and front contact and as relay 425 is only momentarily operated due to the release o'l relay 429 the sleeve circuit isvnow again completed for the reoperation ot' relay 422, and the maintaining of relay 21SA operated. The reoperation ot re'lay'422 closes an obvious circuit tor the operation of relay 431k which is now held opelated. yThe above mentioned cycles ot operations there tore, leave .the circuits in such a condition that in Fig. 4 relays 410, 422, 429, 430, 431, 411, 414 and 421 are operated and lamp 413 is extinguished While in Fig. 2relays 218, '220, 223 and 208 are operated and lamps 200 and 202 are extinguished.

` The operators telephone set is now connected through talking key 401 from the tip conductor of toll line A, through kthe tip terminals"otjack 203 and plug 400, upper middle armature and front contact of relay .411,

' lowerl outer right normal contr-.cts and upper inner left normalcontacts of ringing key 435, right hand upper normal contacts of splitting key 410, armature and front contact of relay 431 to one si deof the operators telephone set and from the ring conductor of toll line A to the ring terminals of-jack 203 and plug 400, lower middle armature and front Contact of relay. 411, lower left normal contacts of splittingkeyi`410', through'normal d contacts of relay 405 to the other side of the operators telephoneset. i After the through operator has received the desiredinformation from the operator at the distant end of toll `line A,she will insert plug 403 into jack 600 of toll line B which is assumed to be the toll line leading to the exchange Where the Wanted subscriber may be found. Theincoming end of toll line B functionsvvith the cord circuit C in the samemanner' as' the incoming end of toll line A did when'it `was connected to the cord circuit C toy cause the operation of various relays and ,A lamps. For example, the relays that will be maintained. operated in toll line B are, 618, 620, 623 and 608, While in cord circuit C lamp 437-is extinguished and relays 441, 462, 444, 439 and 438 are maintained operated. Relay V444 connects Athe onerators tele aliene set to the toll line B so that the toll operator will now be able to talk to the operator at the distant end of toll line B to give lthisoperator the information necessary for the completion of-the connection to the Wanted subscribers line. The talking Connection in this case may be" traced from the tip conductor of toll line B, to the tip terminals of jack 600 and plug iffosetia 403, upper outer armature and front contact of relay 411, upper inner right normal contact of ringing Ykey 435, lefthand upper normal Contacts of splitting key 410, armature and front contact of relay 444 to one side of the operator-s telephone set, while the other side ot' the operators telephone set is eonnected from the ring conductor of toll line B, ring terminals of jack 600 and plug 403, outer lower armature and front contact of relay 411, lower inner normal right hand contacts of ringing key 435, right hand lower normal contact of splitting key 410, through the contacts of key 405 to the opposite side of the operators telephone set.

It should be noted that the operator at the distant end oit the toll line B, may be rung by operating the right hand set of springs of ringing key 435 to apply battery through relay 406 and resistance 407 to the upper outer right contacts of ringing key 435, upper outer armature and front contact of relay 411, tip terminals of plug 403 and jack 600, retardation coil 613, ringing relay 62T to ground. The operation of this relay applies ringing current from the usual source to the tip and ring terminals of toll line B. Having completed the information to the distant operator, key 401 Will be restored.

On the connection ofthe two lines A and B to the cord circuit C relays 430 and 439 are operated. These relays complete a circuit to ground to the position finder E provided the position finder is not in use in connection with any other cord. This ground will start the stepping magnet 500 of cord finder D to operate the finder to hunt for cord C. The circuit for this stepping magnet extends to battery over any terminal of bank 501 on which the brush of this bank happens to rest at the time, this battery being supplied trom the idle or busy cord circuit to which the terminal 501 is connected over the upper outer armaturesv andback contacts of relays corresponding to relays 439 and 430. The only eord that has no battery on its terminal in bank 501 is cord C. This circuit will therefore be completed from battery, brush of bank 501, winding of stepping magnet 500 and its armature and back contact, inner left hand armature and back contact of relay 503` common lead 442. right hand armature and back contact of re-l lay 440, upper inner armature and front contact of relay 439, outer left hand armature and back Contact of relay 445, upper inner armature and front Contact of relay 430 to ground. As the stepping magnet 500 breaks its own circuit it will continue to operate until the terminal of the bank 501 from which battery has been removed is found. This terminal is associated with cord circuit C and the stepping magnet will therefore stop its operation and cause the operation of relay 504. Relay 504` has a high resistance winding and operates in series with the stepping magnet wit'h- Htl lltl

VIS

` to these relays.

win other groups 4o out causing the steppingmagnet to operate.

Relay 50st in operating locks through resistance 505 and itslett hand armature and liront contact to ground and remains in this condition until it is released by the opera tion el' relays 500 and 507 as will hereinatter be described. 'lhe operation ot relay 50e closes an obvious circuit for the operation ot relay 509 which in turn closes a circuit tor the operation of relay 510. `Relays 503, 509 and 510 of' the position finder E are individual to the gro up et cord circuits to Which cord circuit C belongs. Relay 510 will receive battery 'for its cir -uit through a series Circuit over the outer lett hand armatures and contacts et relays corresponding to relay 503 individual to other groups ot cord circuits. The individual relays for cach group et cord eil-cuits corresponding to relays` 503, 509 and 510 are connected in a manner siinila-r 1 Two sets of such relays are shown to 'the left of the group ot relays individual to this position. On the operation et relay 510, an obvious cireuitivill be closed tor relay 503, which by operating" its inner lett hand armature opens the connection 'tor the steppiirY n1agnct500. rlCluisWno other cord in the group of which cord C is one can cause cord finder D to operate until the release et cord circuit C in the manner to be hereinatl-er described. Similarly, the operation et relay 510 by attracting its armature reinores grreruul norniially connected to a chain circuit through the armatures et other relays correspending to relay 510 in other groups, so that none oit the relays corresponding to relay 503 can be operated While relay 510 is actuated. Thus, connections from other cord circuits are prevented from going u'ouggh the position finder until the 'functions o'l4 the cord circuit C are completed.

@n the operation oit relay 503 a circuit is closed tor relay 5l?. as tollows battery, Winding; of relay 51% outer right hand armature 'trent contact el. relay 508, lett hand armature and tirent contact ot relay 504i to ifrouinl. rllhe operation et relay 503 closes a circuit to battery through bank 513 through the cord circuit- C to cause :the operation ot the repeater finder F. This circuit may be traced as follows: battery, lett hand armature and bach Contact of relay 514, inner right han d armature and trent contact ot relay 508, Winding ot relay 515, brush and a terminal ot bank 513, righthand armature and bach contact et stepping inae'net 516 oi repeater `hider l?, lett hand armature and back contact ota relay fle() to the brush et bank 518 et the repeater linder l?. lt the brushes et the repeater finder happen to rest on the terininals ot a busy repeater, which is indicated by the 'tact that ground is connected to the terminals et bank 518, the 'stepping magnet vill start to operate andadvance the brushesot repeater iinder F until an idle repeater is found, which is indicated by the absence of ground on the terminals ot banlr5ltl. ln other worde it a busy repeater is encountered, `ground will be connected to brush 518 through the multiple contacts troni the correspondingbrush et the repeater linderconnected to the busy repeater. rllhis ground will be supplied troni the lett hand armature and irontcontact olf the relays. corresponding to relay lll- 0 in the engaged cord circuits. Relay 515 in the above mentioned circuit a fast operating relay as compared to relay L40 which' is slow to operate. rllhis relay will there'liore prevent relay 140 from oper-actinn1 although a circuit fior relay L140 is completed through the arniature and back contact oit relay 515. This circuit may be traced as follows: battery, lett hand armature and back Contact. of relay 514, inner right hand armature and liront contact ot relay 503, armature and back contact of relay 515, the brush oil the terminal `bank 520, left hain'l Winding ot relay 44:0 to grouiu. rlhe stepping magnet 516 will continue to operate until an idle ii'r-apeater Vtound, that is, one that has no ground on multipled terminale ol" a bank such as 518. The circuit through the relay 515 and the stepping magnet 5l?) will therefore be opened and consequently cause the release of relay 51.5 and the stopping;w oit magnet 516. lWhen this takes place the previously traced Circuit tor relay 4h10 will be completed throuuh the armature and laclt Contact olf relay 515 so that relay 44:0 will now be energized and apply ground through its lett hand armature and trout Contact to the brush 518 thus inalring repeater G busy to other cord circuits. Relay 4:40 in operating provides a locking `circuit tor itsell througrh its right hand armature and ri ejht hand Windinginner upper arinatiure and liront Contact ol' relay 439. outer lett (rniature and haelt Contact oit relay M15 to ground at the inner upper armature and trent eoif" ot relay 450. rllhe operation relay a circuitcor relay as Afollows: battery, Winding; oli` relay 5291.. the selected terminal and the brush ol'banl: 51l le'lt hand arinatureand front contact olf relay i140 to ground. 'lhe operation ot relay 522 proyides ground for the operation oit relay 5111 over an obvious circuit. This latterrelay in operating' rernoves the inultiple battery from the position-finder ll rllhe operation oit relay? battery through the .vindin and 50i7 and its two outer r? also connects or' relays 500 1 hand ernia- 330 and 730 et the switches li and L, respectively, to inarlr these terminals of the repeater tl in the levels on. switches ll and la in which the incoming; and outgoing);.terminals of the repeater .Gr tei inate. The operation ol relay also closes a circuit ttor the operation et relay 525 over a circuit as follows: battery,

CFL

Winding of'relay .525, outer right hand armature and `back Contact of relay .506 or the louter-left hand armature and back contact of relay 507 inner righ-t hand armature and front contact of relay 522 to ground. Relay 525 is common to all repeaters that have their terminals located in the marked levels of the VswitchesK and L and the operation of this relay therefore marks these levels on switches K and L by closing its armatures and front contacts to battery. For switch K the terminal 305 Vis marked with the battery from j relay 525 and for switch L the terminal 705 is marked with the battery from relay 525.

i Theoperation ot relay 440 also closes at its right hand armature and front contact a connection from ground at relay 430 for the operation of relays 450 and 451. The circuit 'for relay 450 may be traced from battery through the Winding of relay 450., right hand armature and front contact of' relay 440 to ground at relay 430A and .the circuit for relay 451 `may be traced from battery, Winding of relay 451, right ha-nd armature and back con- 'A tact of relay 452, through the right hand armature and front contact of relay 440 to ground at relay 430,V The pur-posent .the operation of relay 450.Will become apparent as the description proceeds, The operation of relay 451 closes an .obvious circuit ,tor relay 416. The operation of relay 416 now Adisconnects battery from the cord circuit sleeves by operating its left hand armature and inner .righthandarmature, that is, battery. applied through the windings of relays 414 and 438 .are disconnected. These relays 414 and- 438, however, are maintained operated bythe clo- 'sure of the makebefonebreak contacts of relay 416 to ground through resistances as follows; the `circuit for relay 414 may be traced as "follows: battery, Winding of relayl 414, upper inner normal contacts of key 401, left lhand make-before-break contact ot relay 416,

higl. resistance 454 to ground, While the eircuit yfor relay 18 may be traced from battery, win ding ofrelay 438, lower inner normal con` tact of key 401, ri ght'hand make-betore-break lContact of relay 416 through the high resist- .and B from now on, are practically identical land therefore only the operationsfor linelA,

until these operations differ from the operations of line B, will be described.- Theapplication of ground through the low resistance 457 `to the sleeve of plug k400 causes the re- V`'lease of relay 218,'which in releasing, promesses vides `ground for the operation of relay 216` that is, relay 216 is momentarily operated as relay 220 is slow to release so that on the lease o1 relay 218 relay 216 operates over n eircuit as follows: battery winding of relay 216 right hand arn'lature and front` contact of le lay 220 to ground at the right. hand armature and back contact of relay 218. The operation of relay 216 opens the sleeve circuit to relay 218 and connects the windingr of relay 226 to the sleeve circuit u'l1ich,on finding the ground supplied by the operation of relay 416, operates over a circuit as followsl 'liatteryg winding of relay 226, lett hand armature and hack contact ot this relay, left hand armature and front Contact of relay 216 to ground through the resistance 457 at the left hand armature and trout contact ot relay 416. Relay 226 in operating, provides a locking circuit for itself as lfollows: battery, winding of relay 226, make-beloi'e-break contacts of this relay, lett hand armature, and front Contact of relay 227, inner lett hand armature and back contactof relay 211 to ground. It should be noted that on the original operation of relay 218 an obvious circuit was closed for the operation o1,l relay 227. As this relay is slouto release, on the release of relay 218 a locking circuit is provided for relay 227 as follows: ,attery, right hand windin; r of relay 227 and its right hand armature and front Contact to `ground at the inner right hand armature and front Contact of relay 216. A locking eireuit .is also provided for relay 223 to the ground at the inner left hand armature and back contact of relay 211 `through the left hand armature and front contact of relay 227 so that this relay will not release on the release of relay 218. lVhen relay 216 is again released tl` circuit for relay 218 is restored as will be he ina'fter described and on the operation of this relay, relay 220 isficruieratml and on the operation o'f relay 218 the irst circuit for the operation of relay 227 is reestablished.

*"lherefore, the temporary operation ot rela)` 216 has the eilect of operating relay 226 and this relay locks to the ground at the inner left hand armature and beek contact of relay 211. It should be noted that rela y 226 in operating connects the sleeve. circuit through to the left hand winding of the marginal relay 228. This relay is operated from the "round supplied through the resistance 451 due to the operation of relay 216. The circuit for relay 228 may be traced from battery, left hand Winding of relay 228, left hand armature and tronteont-act ot relay 226, left hand armature and front contact of relay 216, over the sleeve circuit to the ground at relay 416.

As the resistance 457 is low and relay 22S ismarginal in character. relay 228 is operated. It should be noted that in the ease of the operation of the correspondingr relays of line B, the marginal relay 628 which corresponds to relay 228, does not operate as the loo circuit from relay 416 extends through the high resistance 458 to ground. The operation et relay 228 and the non-operation of relay G28 niarks the dillerence between the call originating line A an l the line B to'vvhich the connection is being extended. In other Words, these relays determine` that the line A shall be connected to .the incoming end of a selected repeater G and, that line ll shall be connected to the outgoing end oit a selected re peat .llelay 228 in operating provides a locking circuit for itself through the inner lett hand armature and back contact of rcay en.

ris stated, the functions of the circuits for lines Av and B are practically identical eX- cept ttor this marking` el the lines and as this applies also to the functions of the repeater finders K and L only theoperation of the linder ll. to connect line A to the incoining end ot repeater G will be described, While the description of the connection of line B to l e outgoing` end of repeater Gr through link li will be abbreviated.. l/lilhile the above inentioned operations of the circuits of the line ril take place, relay Zl52 in the cord circuit (l is operated over a circuit as follows: battery, winding oit relay 4.52, outer right handarinature and 'liront contact ot relay lll@ to ground. yThis relay is locked through its right hand armature and front contact to ground at the inner upper armature and front contact of relay 430. Relay 4:52 lin operating causes the relase oit relay el which in turn releases relay elli so that the sleeve circuits are new restored to their normal condition. to allow, in this ,ase, the reoperation ot relay 218 hereinbel'ore inentioned on the release or' relay The release of `relay 216 connects battery through armatures and contacts ol relays 220 and 22S to the winding of relay 231 and to the stepping magnet 300. The circuit tor the stepping magnet 300 may be traced as lollows: battery, outer right hand armature and back contacts of relay 2lG, outer right hand armature and front contact of relay 225, winding oit the stepping magnet and its armature and back contact to the outer lower armatiu-e and back contact of relay 237, upper armature and back Contact et' relay 231 to ground. The circuitjlfor relay 231 extends ii'roni battery, the outer right hand arinature and inner back contact of relay 210,1ett band armature and liront Ycontact oit relay 228, inner right hand armature andfront contact ot relay 220 through the Winding of relay 231 and to the brush of bank 301 ot the trunk selector lil. Provided this selector is not rest' on an idle trunk connected to a repeater linder such as K having access to the incoming end of repeaters, the stepping ni Qjnet Willoperate, that is, it the brush o'i bank 2301 is in contact With terminals that eitherare open or connected tobattery as will hereinafter be explained. The selector 1will continue to step over idletrunks leading to repeater linders suchas M having access to outgoing ends of repeaters and busy trunks of this type and also busy trunks such as are connected to recpater finders like K having access to the incoming ends of repeaters. ln case ol busy repeater' finders such as M and K, relays 302 and 30a are in Operated condition, so that the terminals ol the bank 301 that lead to the inakebeiiorebreak contact of these relays are opened. ln the case oil? idle trunks having access to repeater liuders such as M, the terminals l'or these trunks at the bank 301 are connected to battery, through the inake-belore-break con,- tacts and windings of relays such as 304. ln either case therefore, the stepping niagnet 300 will continue to operate until an idle trunk such as the one connected to repeater finder K will be encountered. lVhen this Lakes place the ground connected through the Winding ot relay 302 and the niake-beforebreak contacts ot this relay will cause the operation ol relays 28l and 302. The cour plete circuit ilor these relays may be traced as follows: battery, outer right hand armature and back contacts of relay 210, lett hand armature and front contact of relay 228, inner right hand armature and front contact ot relay 226, Winding ot relay 231, lower armature and back contact` of relay 230, brush oi? bank 301, 1nake-beforebreak eontacts of relay 802, Winding of relay 302 to ground.- `Relay 231 in operating removes the ground lroni the stepping magnet circuit thus stopping the brushesof the selector l-I on the terminals of the idle trunk. Relay 231, also by operating `closes an obvious circuit tor the operationiof relay 2237. Re lay `237 in operating closes a circuit `tor relay 236 as follows: battery, Winding et relay 237, winding of relay 236, lower armature and 'trent contact of relay 237, left hand armature and iront contact ot relay 227, inner lett hand armature and back contact of relay 211 to ground. Relay 236, however, does not operate at this time as it is shortcircuited by the groi'ind connected to the upper armature and front contact ot relay 231. l'lllhen relay 302 operates it disconnects its winding `trein the terniinal ol bank 301 and provides a locking circuit toritself as ttollosvs: battery, 11th step rotary contacts 300 under control ot finder lsv., armature and back Contact of relay 307, right hand armaturey and :trent Contact and Winding of relay 302 to ground.` lhe reinoyal ot the ground 'from the terini nal ot bankBOl. releases relay 231A which when releasing ren'ioyes the shortcircuiting ground troni the circuit for relay 230, allowing this relay to operate in series with the relay 237. The circuit for the stepping inagnet 300 is held open by the opera tion of relay 237.

In case a trunk connected to repeater finders such as M or L having access to the outgoing-ends ofrepeaters had been desired, ground instead of battery would have been connected to the winding of relay 231. This is exactly the function in the case of relay G31Vfor line B. It will be note'd that this ground will be supplied by relay 616 through the outer right hand armature and back contact of relay 628, inner left hand armature and front Contact of relay 626 and in this case relay 704'will operate when the brush of bank 7 01 encounters ,battery through a trunk connected to a repeater finder such as L having vaccess to the outgoing end of repeaters. Consequently the fact lthat relay 028 1s not operated causcs the trunk selector I to select a trunk connected to a repeater finder such as L having access to the outgoing end of v repeater G.

Returning Anow to the operation ot the rel peater finder K tlre operation of relay 236 opens the'lelad from the brush of bank 301 thus making the selected trunk busy. vThe operation of relay 237 closes a circuit for the operation of relay .238 as follows: battery, winding of relay 238, armature and back conknown expedient for securing a good connection `between brushes Vand terminals of switches. The connections established from the ringing source 2210 through the armatures "and rontcontacts of relay 238, brushes and terminals of banks 310, 311, 312 and 314;, the armatures and front contacts ofrelay 316 and thebrushes and terminals of switch K to the incoming leads of repeater G are suiiiciently ,clear torequire no further description.

` The operation of relay 302 of the circuit arrangement for repeater inder K provides a circuit forthe 'operation of relay 318 as tollows:fbattery,.winding of relay 318, armatures andback contacts of the rotary magnet 319 and the vertical magnet 320, left hand armature and front Contact of relay 302 to ground. The operation of relay 318 closes a circuit for thevertieal magnet 320 as follows: battery,iarma-ture and front contact of relay 318, right hand armature and back contact of relay 322, Winding of vertical magnet 320, outer 'right hand armature and back contact of relay321, to ground at the left hand armature and front Acontact of relay 302. The

l kalternate operation and release of the vertical magnet 220 and the relay 318 will now take place and the vertical magnet 320 Will therefore now step the brushes of the repeater finder K upward to the level in which the terminals of the repeater G selected by the cord circuit C may be found, that is, until the battery on the contact 305 is encountered by the brush W'hen this level is reached, relay 322 will operate over a circuit as follows battery, outer lett hand armature and front contact of relay 525, terminal 305, brush 326, right hand winding of relay 322, outer right hand armature and back contact of rela-y 321 to the ground at the left hand armature and front conta ct of relay 302. The vertical magnet will thus bc prevented from operating further and the battery at the armature and trout contact of relay 318 will be transferred through the right hand armature and front Contact of relay 322 to the rotary magnet 319 and the circuit for the vrotary magnet will thus be completed from the above mentioned battery to the ground at the left hand armature and front contact of relay 302. Relay 322 upon operatin g closes a locking circuit for itself trom battery through its left hand armaturcand front contact and left hand wind ing to thc ground at the left hand armature and front contact of relay 302. The rotary magnet 319 will now operate to step the brushes of the finder K around on the selected level to the terminals of the desired repeater G, which have been previously marked by the operation ot relay 522 as hereinbeforc described. lVhcn the brush 331 of finder K makes contact with the ma rkcd terminal 330, relay 321 will be operated over a circuit as follows: battery, windings of relay 506, outer right hand armature and front contact of re- .lay 522, terminal 330, brush 331, right hand winding of relay 321 to ground at the upper closed contacts of the vertical off normal contacts 333. Relay 321 in operating, opens the circuit for theA rotary magnet 31!) and also causes the release ot relay 322 since the circuit for this magnet and relay is opened at the outer right hand armature and back contact of relay 321. Relay 321 in operating provides a locking circuit for itselfl before any of its other contacts close from the ground 'at relay 302 through its outer right hand armature and front contact and leift hand winding to battery. The operation of relay 321 closes a direct connection to ground independent of the right hand winding of this relay through its inner right hand armature and front contact for the operation of relay 506. The terminal 330 of the repeater G is thereby made busy to other repeater finders. Relay 506 does not operate at the same time as relay 321, since the current through the winding of relay 321 is insufficient to operate relay 506 while its active winding is shunted by the battery through its non-inductive left hand winding. The operation of relay 321 closes an obvious circuit for the operation of relav 316. The operation of this relay closes the llo transmission leads from the trunk selector H through repeater inder K to the leads ot the incoming end of repeater G. It is at this time that the ringing current from source 240 is connected to the repeater 'for burning out the brushes and terminals of selector H and linder- K.

The line B is connected to the outgoing end ot repeater G in the saine manner as line A is connected to the incoming end ot repeater Gr as previously explained. In this case the connection will, ot course, extend through the trunk selector I and the repeater finder L. llllhile the operations of the switches I-I and K and I and L may begin simultaneously, it is evident that these switches will not complete their operations at the same time as they may have to travel ditlcrent distances to liud their respectively marked terminals. Not until bot-h relays 506 and 507 are operated will turther circuit-s to complete the connection be effective. When these two relays operate, a circuit will be closed `for relay 528 as itollows: battery, winding et relay 528, makebetore-break contact ot relay 530', outer right hand armature and front Contact et relay 507, outer left hand armature and trout contact oit relay 506 to ground. The operation of relay 52S closes an obvious circuit tor the operation ot relay 529 and this relay in operating closes an obvious circuit for the operation ot relay 530. Relay 530 in operating locks at its `lett hand armature and front contact to the ground at the outer left hand armature and trent contact et relay 506 and opens at its malte-betore-break contact the circuit 'for relay 528, which in releasing opens the circuit lor relay 529, which in releasing opens the original energizing circuit for relay 530. As soon as the toll operator has iinished her conversation with the operator at the distant end ot' line B, relating tothe extension ot 'the connection, she will restore the telephone key 401 and in so doingcause the release of relays 421 and 411. When relay 4:21 is released a circuit will be completed tor the operation of relay 531 as follows: battery, upper outer armature and back contact ot relay 421, outer lett hand armature and front contact oi relay 4h52, bank 533 of repeater lin-der F, left hand armature and bach contact ot relay 529, right hand armature and trent contact et relay 530, lett hand winding of relay 531 to ground. The operation oit relay 581 removes the usual short circuits from the bridge points of the repeater Gr and prepares the repeater tor transmission. lIhis cycle oit operations just described for relays 52,8, 529 and 530 serves as a means for allowing time for the burning out ot the contacts ot' the selectors H andV I and repeater finders K and L as hereinbetore described betere the repeater Gf is actually ineluded in the connection, that is, there is a certain interval before relay 531 is operated alter the connections have beenfcompleted -trom lines A and B to the repeater G. It should be noted that a circuit is also closed :trom the battery at the upper outer armature and back contact ot relay 421 through contacts ot relays 529 and 530, 522 and 514; l'or the operation of relay 239 ot the circuit iter line A and also a corresponding relay 6239 olf the circuit for line B. The operation ot these relays removes ringing current `from the contacts ot the switches H, K, I and L by causing the release et relays 238 and 638, respectively. The release ot the relays 238 and 038 close circuits trom battery, at the upper outer arma ture and back contact ot relay e121 to the winnt ings ot relays `242 and 642. These relays in operating disconnect the talking conductors of toll lines A and B, respectively, 'from the cord circuit C and connect these lines and their respective networks hl, and N2 to the repeater through the connections set up by the selectors H and I and repeater lnders K and L. The connection trom lines A and B through the repeater G is now completed for transmission purposes. It seems unnecessary to trace the circuit 'fromone line to the other, as it is quite obvious from the drawing how this connection is made.

It might be explained here that it, durin the vertical movement of the finders K or L, the marking et tl e terminals such as 305 or 705 should for some reason or other not be identified by the brushes 326 or 726 et the finders K or L, the vertical magnets 320 or 720 would continue to step the brushes up until` the tenth level is reached, at which time relay 322er relay 722 will operate from i the battery which is supplied permanently at the tenth level to brushes 326 or 726. In this case rotary magnet 319 or 719 would operate to step the brushes over this level until the 11th rotary step is madeat which time the brushes would actuate the 11th step rotary contacts 306 017706. The operation oit these contacts would cause the operation ot the re- `lease magnets 325 or 725 over obvious cir cuits so that these switches would be restored to their normal positions. In the case of switch K, Ll'or example, the vertical eti normal contact-s are closed. The release magnet will be held operated by a circuit from battery through the release magnet, operated vertical oli normal contacts to ground at the lett hand armature and back Contact oi relay 302. It will be noted that the locking circuit for relay 302 will be opened by the 11th step rotary contacts 306 and relay 302 will remain released until the vertical off normal contacts are restored to normal.

The time alarm circuit T operates as lollows: 0n the operation ot relay 512 a circuit is provided 'for the operation of stepping magnet 536 as follows: battery, outer lett hand armature `and back contact of relay 537. armature and back contact and winding of stepping magnet 536, outer right hand armallO ture and back Contact of `relay 537 to ground at the outer left hand armature and front contact of relay 512. lVhen the stepping magnet 536 operates to move the brushof bank 538 one step this brush connects with a terminal connected to ground andthe relay 537 is operated over a circuit as follows: bat

, tery, inner left hand armature and :front contact of relay 512, winding of relay 537, makebelore-break contact of this relay, winding ot magnet 536 to ground at the lirs't terminal of bank k538. vRelay 537 locks up to the .ground at the outer left hand armature and front contact o1" relay 512. Relay 537 1n operating provides battery tor theoperation of relay 54.0 through interrupter 541. Relay 540 in operating closes a. circuit for the operation of stepping magnet 536 as follows: battery, outer leitt hand armature and front contact of relay 537, armature and front contact of relay 540, winding of stepping magnet536, brush of bank 538 toy ground at the -rst terminal.- The interrupter 541 causes relay 540 to alternately operate and release. That is, the battery at its armature and 'trent contact will be alternately connected and removed from the circuit' for the stepping magnet 536. y The stepping'magnct therefore advances brushes of banks 538 and 542 step-bystep under the control of interruptor 541. If this condition prevails 'for a. eertain yperiod, for example. for tiverseeonds, the brushes Willhave been advanced to a predetermined .'position. An alarm will then be given and the position finder and cord finder will be released to prevent holding up the system. It,

for example` for some reason or other the system has failed to function in this period, the brush of thebank 542 will be advanced to Aterminal543. In this position ground from the inner left hand armature and front contact/of relay 5,37 will be connected through termina-l 543, the inner lefthand armature and front Contact of relay 512, the brush of bank 545 through' the winding of relay 445 vto battery. rRelay 445 operates and locks underv control of a key 460 and causes the re'- lease of theV cord linder Vand position finder. This is accomplished by plaein g battery'from the middle left hand armature and front contact of relay 445 on the brush of bank 501 to release relay 504 and thus cause the release ot relays 509, 512 and 510 and 503 in suecersion to release the positioninder E. The operation of relay 445 also closes a circuit at its outer right khand armature and front con# tact fromv battery, through lamp '461. to ground through the winding ot relay 562.

.Lamp 461 lights and indicates to the operator that the circuit has failed to function properly andthe operation of relay 562 closes a circuit tor relay 563 to an interruper 464. The operation of relay 562 also closes a circuit for an alarm bell 565 which is common to the otHee in vwhich the toll operator is located.

`The operation of key 460 will restore the circuit to normal condition.

Assuming, however, that the repeater is ,inserted-in the connection within the allotted time, the time allowance circuit will not funetion to give an alarm. since relay 512 is released as will hereinafter be described. Rclay 512 in releasing causes the release of relay 537 which closes a circuit for stepping magnet 536 to advance the brushes ot banks 53S and 542 to the next position marked by terminal 543 or 545 and thus prevent an alarm lroin being given. i

In ease all ot the repeaters are busy. battery through bank 513 of cord finders such as D will not be available as all relays such as 514 will be actuated. However. battery through the high resistance windingr of relay 550 of the common meter circuit R will be available. The high resistance of the. winding ot relay 550 will prevent relays. such as 440, from Vbecoming operated but will allow the operation of relays 550 and 460 as follows: battery, winding of relay 550, inner right hand armature and front contat-t of a relay such as .103, armature and back contact; of a. relay such as 515, a bank such as 520, winding ot a relay such as 440 to ground while the circuit for a relay such as 460 will be as follows: battery. right hand winding o't` a relay such as 469, a bank such as 552. inner right hand arnlatul'e and front contact ot a relay such as 503 to ground through the right hand winding of relay 440. On the operation of relay 550 a circuit will be closed for the operation of the meter magnet. 553 when the timing device operates to indicate or count the number of times repeaters were required that were not available due to the tar-t that all repeaters were busy. 1tshould he understood that in case a repeater becomes idle bc'lore the timing device operates the eircuit will function to select this repeater in the manner hereinbe'lore described. Relay 409 in operating closes a locking circuit for itself through its right hand armature and front Contact to the ground at the inner upper armature and front Contact of a. relay such as 430. The operation of this relay also closes a circuit from the interruptor 464 to the lamp 437 and this lamp is now Hashcd to indicate that no repeater is available. lVhen a plug such as 400 or 403 is removed. lamp 437 stops flashing. as it should be understood, that the above operations take place in the cord that hasbeen taken for use in establishing a connection, when it is found that a repeater was not available.

It the operator has occasion to aetuate the talking key 401, after the repeater G has been connected between lines A and B, relay till 421 will be reoperated releasing relay 531 and relays such as 242 and 642. The release ot relay 531 short-circuits the bridging points ot the repeaters used and the release ot relays 242 and 642 disconnects lines A and B and their respective networks troni the repeater Gr and connects them to the cord circuit and to the operators telephone set. [is the bridge relays such as 205 and 605 are not disconnected trom the cord circuit supervisory signais may be received over the toll lines.

The operation when either ot the plugs is removed is substantially the same. For example when plug 400 is removed from toll line A, relay 218 is released. This causes a momentary operation of relay 216 through the right hand armature and iront contact of relay 220 which is released soon atter the release ot relay 218. On the operation oi relay 216 the remaining operated relays oit the circuit ior toll line A are restored to normal such as relays 237, 286, 223, 226, 4227, 4228 and 208. In the cord circuit C relay 4114 is released and this relay in turn releases relay 30. The release ot relay 430 connects bat tory trom the armature and iront contact ot relay 450 to the ring conductor ot the cord to cause the operation of relay 611. rEhe operation of relay 611 removes ground i'rom the locking winding ot relays 608, 626 and 628 while relays 623 and 620 are held operated by relay 618. Relay 450 of the cord circuit releases through the release oit relay 430 and consequentlyfrelay 611 will be operated only momentarily. The release oi relay L1:80 by opening the common ground applied at its inner Vupper armature and trontcontact also causes the release oft relays .440, 452, 522, 506, 507 and 531. The release ot' relay 522 applies battery 'for the operation oit the marginal relays 307 and 707 of the repeater finders K and L, respectively.V Theserelays are operated only on this battery :trom the outer lett hand armature and baclrcontact ci relay 422. Relays 307 and 707 in operating open the holdingl circuits tor relays 802 and 602 and these latter relaysin releasing` causethe restoration ot' the repeater linders K and L to normal as hereinbetore described. Vhile the present invention has been described. as particularly applicable to toll systems it may also vbe applied to switching vsystems not operated on the tollbasis.

What is claimed is:

1. In a telephone system, lines, means tor selecting any two oi. said lines, repeaters arn ranged vtor interconnection between selected lines, selecting devices individual to said lines tor selecting` a repeater, and means operable in response to the selection ott two lines tor simultaneously actuating the individual devices of said two lines tor interconnecting a repeater therebetween.

2'. ln a telephone system, lines, means for selecting et said lines, rinl ters,

,lecting devices associated with each oli' said lines i'or interconnecting a repeater between selected lines, and means operable in response to the selection ott' two lines tor controlling two ot said. selecting devices simultaneously whereby one selected line selects one end ot the repeater while the other selected line selects the other end of said repeater.

3. In a telephone system, lines, repeaters, cord circuits, selecting apparatus associated with each ot said lines and operable simultaneously for interconnecting a repeater between any two ot said lines, and means responsive to the connection ol? a cord circuit between two ot said lines tor controllingthe selecting apparatus.

et. In a telephone system, lines, repeaters, cord circuits, selecting apparatus associated with each ci; said lines tcrinterconnecting a repeater between any two ot said lines, means responsive to the connection ot one end et a cord circuit to one line and to the connection ot the other end ot said cord circuit to another line tor actuating the selecting apparatus of said iirst mentioned line to connect the incoming end oi' a repeaterthereto and tor actuating simultaneously the selecting apparatus of the second mentioned line to connect the outgoing end olf said repeater thereto.` y y 5. In a telephone system, lines, repeaters,

a selector switch associated with each line,

two groups oi trunks accessible by said switches, a finder switch associated with each trunk, the finders ot' one group of trunks having access to the incoming` ends of said repeaters while the finders oi the other group have access to the outgoing` ends ot the repeaters, means tor operating the selector switch oi one ot said lines to select an idle trunk leading to a finder having access to the incoming ends ot the repeaters, means tor operating the finder associated with such trnnlrto hunt tor and connect said linewith the incon'iing end of an idle repeater, means to operate the selector switch oit another of said lines to select an idle trunk leading to a iinder having access to the outgoing ends ott therepeaters, and means to ope 'ate the finder associated with said last mentioned trunlr to hunt 'for and connect said second line with the outgoing end ot said idle rcpeater.

6. In a telephone system, lines, repeaters,

cord circuits, a selector switch associated with each line, two groups of trunks terminating in said switches, a line .finder connected to the -,tree end ot each trunk, the line finders ot one group et trunks having access to the incoming ends o1 said rei'ieatcr, while the line linders ot the other ,group ont trunks have access to the out-gefng` end ot said repeaters, means responsive to the interconnection of a cord cirenit between two ott saidlines for operating l lim 

